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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

It's easy to understand why Lindzen insists on repeating this myth, because it's the basis of his argument that climate sensitivity (the amount the global temperature will change in response to increasing CO2, including feedbacks) is low, which in turn is the lynchpin for all climate contrarianism. However, despite its importance to Lindzen and his fellow climate contrarians, it is simple to show why Lindzen's "Earth should have warmed more" argument is wrong along every step of the way.

1.Lindzen claims"We’ve already seen almost the equivalent of a doubling of CO2 (in radiative forcing)."

In reality the net radiative forcing is most likely less than halfway to the equivalent of a doubling of CO2.

2.Lindzen claims "that [radiative forcing] has produced very little warming"

In reality the amount of warming we've observed is consistent with a climate sensitivity in the range cited by the IPCC.

3. Lindzen concludes that his argument proves climate sensitivity must be low.

In reality aside from Lindzen's arguments being wrong, the full body of evidence points to much higher climate sensitivity than Lindzen believes.

1) Halfway to Doubled CO2

Lindzen's claim that we have almost reached the equivalent radiative forcing (global energy imbalance) associated with a doubling on atmospheric CO2 is based on cherrypicking. Quite simply, he is only looking at the radiative forcing associated with CO2 and other greenhouse gases (GHGs), ignoring all other radiative forcings. The problem with this is that the climate responds to the net radiative forcing, not just to GHGs.

Even ignoring other radiative forcings, Lindzen's argument is still wrong. According to the NOAA Annual Greenhouse Gas Index, the GHG radiative forcing (relative to 1750) in 2010 was 2.81 W/m2 - only 76% of the way to doubled CO2-equivalent.

However, the second-largest single radiative forcing (behind CO2) is most likely associated with aerosols, which have a strong net cooling effect by blocking incoming solar radiation both directly and indirectly (by seeding clouds). There is also an associated warming effect from black carbon, which darkens the planet's surface, causing it to absorb more incoming solar radiation. As Lindzen notes, the overall magnitude of these three effects is highly uncertain, but Lindzen approaches this uncertainty incorrectly by treating aerosols as if they have zero forcing with zero uncertainty. In reality there is a wide range of possible values, which according to the 2007 IPCC report lies between -0.2 and -2.7 W/m2, with a most likely value of -1.1 W/m2 (Figure 1). Note that Lindzen's assumed value of zero for the net aerosol forcing falls outside of this range.

Figure 1 also gives the range of likely values for the net radiative forcing in 2005 (with respect to 1750), which ranges from 0.66 to 2.7 W/m2 with a most likely value of 1.72 W/m2 (anthropogenic plus natural). The radiative forcing associated with a doubling of atmospheric CO2 is approximately 3.7 W/m2; therefore, we are between 18% and 73% of the way to the equivalent of a doubling of atmospheric CO2, with a most likely value of 46% (although the net forcing has continued to rise since 2005 due to continued human GHG emissions, so we are now in the ballpark of 50%). Note that the maximum value here (73%) is well below Lindzen's claim that "we’ve already seen almost the equivalent of a doubling of CO2."

Thus when we consider all influences on global warming, it becomes clear that Lindzen's claim that we are near the equivalent doubling of CO2 is most likely wrong by a factor of two.

2) Earth Has Warmed as Expected

In addition to the influences of non-GHG radiative forcings, the thermal inertia of the oceans is another effect that Lindzen has completely neglected.

Due to the fact that much of the Earth is covered in oceans, and it takes a long time to heat water, there is a lag before we see the full warming effects of any radiative forcing. In fact, we know there remains unrealized warming from the GHGs we've already emitted because there is a global energy imbalance. The amount of unrealized warming is dependent upon the amount of CO2 in the atmosphere (or other radiative forcing causing the energy imbalance) and the thermal inertia of the oceans (which causes a lag before the warming is realized). In fact, Lindzen admitted as much in his 2005 testimony to the UK Parliament House of Lords Economic Affairs Committee, explaining:

"the oceans' heat capacity leads to a delay in the response of the surface"

Lindzen proceeded to argue that this delayed response was insufficient to explain the difference between observed and expected global warming, but this is simply wrong as well. In reality, most past climate models with climate sensitivities consistent with the IPCC range predicted the subsequent global warming with a high degree of accuracy (Figure 2).

As Figure 2 shows, the Earth has warmed consistent with climate scientists' expectations.

3) Climate Sensitivity is Relatively High

In the end, Lindzen's argument that climate sensitivity is low because the Earth hasn't warmed as much as expected is wrong because he overestimates the net radiative forcing by a factor of two and ignores the thermal inertia of the oceans.

However, we should also note that there is a very large body of climate sensitivity research using many different lines of evidence, all of which point to a sensitivity in the range cited by the IPCC (Figure 3).

Figure 3: Distributions and ranges for climate sensitivity from different lines of evidence. The circle indicates the most likely value. The thin colored bars indicate very likely value (more than 90% probability). The thicker colored bars indicate likely values (more than 66% probability). Dashed lines indicate no robust constraint on an upper bound. The IPCC likely range (2 to 4.5°C) and most likely value (3°C) are indicated by the vertical grey bar and black line, respectively. Adapted from Knutti and Hegerl (2008).

Lindzen's Double Standard

In a moment of irony, at one point in his Sandia Labs presentation Lindzen claimed that for 30 years, climate scientists have been "locked into a simple-minded identification of climate with greenhouse-gas level," claiming that climate researchers have effectively ignored all non-GHG climate influences.

Climate scientists have focused a lot of research on the climate effects of aerosols, black carbon, solar irradiance, volcanoes, natural cycles, and many other climate influences. Lindzen's criticism of climate scientists ignoring non-GHG effects has no basis in reality, but it quite accurately describes his own arguments.

Lindzen's Repeated Errors

The mistakes Lindzen keeps making in his presentations are not complicated ones. Ignoring all non-GHG forcings and the thermal inertia of the oceans are two glaring errors which any good climate scientist should immediately recognize. On the contrary, Lindzen has been making these same wrong assertions in talks since at least 1989, and has continued making them at minimum on an annual basis since 2002.

This behavior is simply unacceptable. Every time Lindzen gives a climate talk, he is misinforming his audience by repeating these indisputably wrong claims. Until he corrects these errors, Lindzen is doing a disservice to every audience that invites him to speak.

While Sandia Labs sought to "shed light on the wide spectrum of thought regarding the causes and extent of changes in Earth’s climate", unfortunately Lindzen has instead spread the darkness of long-debunked myths and misinformation.

Comments

Excellent summary. Having been apalled by witnessing first-hand his apparently deliberate attempt to peddle misinformation in London in February this year, I tried and failed to get him to explain his "scepticism". I then tried and failed to get either the MIT or the AGU to extract the same from him. I am therefore very disappointed to see that, just months away from retirement to the south of France, he is apparently still peddling exactly the same misinformation. Clearly, my inability to get anyone to call him to account and/or reign-in waht appears to be deeply-prejudiced and unprofessional behaviour has merely served to convince him that he can do just as he pleases without fear of any adverse consequences).

The NY Times has an article which mentions that Lindzen is looking forward to retirement, possibly at his second home. It struck me as a biased piece.

Honestly though, he hasn't said anything new for a while, and that hasn't stopped him from being a sceptic magnet. So, I don't know that his retirement would make any difference. Even if he becomes not topical, some other contrarian will feel the void.

Lindzen has credentials though. He's been in the field for a long time and has a lot of publications. People don't care that he's always wrong or always repeating the same misinformation, because they can say "this climate scientist from MIT says it's nothing to worry about". It would be nice if Lindzen would do us all a favor and retire and stay out of the media.

The forecast retirement of Lindzen brings to mind that contrarian climatologists are an ageing lot, as are those non-climatologists who are in the vanguard of the faux sceptics movement.
Perhaps there is an increasing relevance in Max Planck's 1948 observation that "a (new) scientific truth does not triumph by convincing its opponents and making them see the light, but rather that its opponents die and a new generation grows up that is familiar with it". [my brackets]

The question is what impact his presentation made. I have seen Lindzen giving presentations, and -- not unlike Monckton -- he is a versed public speaker with reassuring demeanor. That is why it is important to spread the debunkings as they are much more difficult to make on the spot in response to a presentation. The presenter is usually the incumbant, working from a higher vantage point and with time on his/her side, and his/her message will be better remembered than critical questions from the audience. That is why institutions need to be careful when inviting him and others, and follow up with debunkings such as the above if they are really skeptical about Lindzen.

krisbaum, it's not clear to me what your point is, or that you understand much about climate science. I'm no expert either, but it looks to me like your questions and insinuations are based on ignorance and ideology rather than scientific or skeptical enquiry. Perhaps you mean climate sensitivity not climate forcing. And perhaps you mean degrees celsius (C) rather than cents (c).

Krisbaum - the IPCC reports are assessments of the peer-reviewed scientific literature on climate. It doesn't get any more definitive than that.

As for sunlight-reflecting aerosols, they remain somewhat of an unanswered question. We don't really know how much further warming they are masking on a global scale because their main climatic effect is that they alter cloud properties (indirect effects). We do know, however, that there was a dimming of surface solar radiation in the Southern Hemisphere in the last decade, and that locally aerosols can dramatically alter sunlight reaching the surface in areas of high pollution - such as the brown haze that extends out over India into the Indian Ocean.

The GLORY satellite was going to help answer the question of aerosols & climate, but it sadly crashed and burned soon after launch last year. A new mission won't be up and running for a while now - assuming another mission gets the OK

Assessments of peer reviewed literature - so what?.. have you asked these questions;

a)who does the reviewing?
b)are they impartial to the results?
c) (-Snip-)

the IPCC contains a lot more than 'peer reviewed' by the way. It contains news links, WWF report links, un-peer reviewed paper references - to name a few..over a 3rd are from these types of sources.

(-Snip-)

(-Snip-)

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Moderator Response: [DB] Ideological, intimations of impropriety and inflammatory snipped. Pleas take the time to ensure your comments are constructed to be in compliance with this site's Comment's Policy as future comments constructed as this one will be summarily deleted. FYI.

Oh and by the way, you've just proven my point by outlining the Aerosol problem and the lack of knowledge. Historical records are non-existent and something of a mathematical formula relating economic prosperity to energy consumption and therefore pollution has been used as a rough idea.. Give me a break!

krisbaum, regarding aerosol literature, as KR notes, the IPCC is the best place to start as the definitive summary paper of the state of climate science. Skeptical Science has also written a number of posts on more recent aerosol research, if you use our search tool.